1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device, and more particularly, to a method of manufacturing a semiconductor device capable of improving a retention characteristic in case of a flash memory device, in such a manner that a gate is formed on a given region of a semiconductor substrate, spacers are formed using DCS-HTO or TEOS, and hydrogen remaining within the spacers are removed and nitride films are formed on the spacers at the same time, by implementing a RTA process under nitrogen atmosphere.
2. Background of the Related Art
A prior art method of manufacturing a semiconductor device will be described taking the flash memory device of FIG. 1 as an example.
A stack gate on which a tunnel oxide film 12, a first polysilicon film 13, a dielectric film 14, a second polysilicon film 15 and a tungsten silicide film 16 are sequentially stacked is formed on a given region of the semiconductor substrate 11. At this time, the first polysilicon film 13 serves as a floating gate, and the second polysilicon film 15 and the tungsten silicide film 16 serve as a control gate. Next, spacers 17 are formed at the sidewall of the stack gate using DCS-HTO. An impurity ion implantation process is then implemented to form junction regions 18 in given regions of the semiconductor substrate 11.
In the flash memory device manufactured by the above process, a charge retention characteristic greatly influences a reliability characteristic of the device. Today, as DCS-HTO and a Si2H2Cl2 source gas are employed in order to form the spacers in the flash memory device, hydrogen exists within the spacers due to reaction such as [Chemical Equation 1].Si2H2Cl2+N2O→SiO2 (spacer)+H2 (trap within the film)+Cl↑  [Chemical Equation 1]
In particular, since the annealing process is implemented in a subsequent furnace equipment for a long period of time, it is much easy for hydrogen to diffuse into the film constituting the stack gate. This hydrogen is trapped inside the film constituting the stack gate and is diffused into the tunnel oxide film by a subsequent annealing process. Hydrogen existing within the tunnel oxide film forms Si—H bonding. Electrons that are moved in the future program and erase operation are neutralized by hydrogen in the tunnel oxide film to cause a charge loss phenomenon. As a result, a charge retention characteristic that is most important in the flash memory device is degraded.